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Comment by nullc | Hacker News Reader

oh... now I understand the purpose of the TDMA. Using actual optical switching to interconnect. Very interesting!

Got any pointers to the sort of optical switching components you're using?

[I've been out of the networking business professionally for almost a decade now, so I'm a bit out of touch with the state of the art in optical stuff--- I was somewhat surprised recently to learn of the existence and low cost of LR4 40gb optics. :P]

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That's part of the research we're doing!

Take a look at: https://circuit-switching.sysnet.ucsd.edu/

And: https://arpa-e.energy.gov/sites/default/files/UCSD_Papen_ENL...

The current generation of switches that we're working on uses diffraction gratings patterned onto glass hard drive platters, installed in a modified hard drive, spun by a custom motor controller that's synchronized to the NICs via PTP.

Ha. I was going to guess it would be an AOM, I wouldn't have guessed a diffraction grating on a hard drive platter. That's awesome, and must be incredibly energy efficient.

The cost of switch ports and interconnects could all be dumped into making host interfaces faster, allowing for the switching time to be reduced.

What are the losses between ports that you are experiencing and what is the crosstalk between ports that are not connected?

Crosstalk is better than 30 dB, and double pass loss between ports is 5-8 dB. The switch is basically cycling through three or four different interconnection patterns that are defined by looped back fiber connections, so the signal has to pass through the switch twice.

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